Detection and Tacking of Faces in Real Environments by R. Herpers et. al. from International Workshop on Recognition, Analysis and Tracking of Faces and Gestures in Real-Time Systems, 1999, IEEE Proceedings describes basics of facial detection and recognition software for general applications.
Xuming He presented an ARVO poster in 2011 describing a system for a visual prosthesis that automatically zooms in on a face in a visual scene to help a visual prosthesis user identify the face.
US Patent Application 20080058894 for Audio-tactile Vision Substitution System to Dewhurst describes providing visual information to a vision impaired person using audio or tactile information including information regarding facial characteristics.
International patent application WO 20010384465 for Object Tracking for Artificial Vision by Barns et al. describes a system for tracking objects, such as a face for a visually impaired user.
US Patent application 20130035742 for Face Detection Tracking and Recognition for a Visual Prosthesis, the disclosure of which is incorporated herein by reference, is by the present applicants and describes a system for identifying a face and indicating is location to the user of a visual prosthesis.